A Simple and Colorful Experiment to Show Nanowire Membrane Construction for Molecule Separation

A chemistry laboratory experiment is described to introduce undergraduate college students to membrane separation technology. This experiment combines a simple nanowire membrane fabrication and visually indicated molecule separation. The membrane is produced via coprecipitation synthesis followed by a filtration assembly process, which can be carried out with ease within 1 h. Molecule separation using membrane filtration is then illustrated by filtering solutions containing methylene blue (MB), rhodamine B (RhB), and an MB/RhB mixture, respectively. A comparison of the filtration results displays that the membrane preferentially rejects MB molecules, whereas the RhB molecules easily pass through it, leading to an impressive separation efficiency of dissolved MB molecules from the dye mixture solution. The clearly visible color changes occurring before and after filtration trigger students' interest in advanced membrane separation technology and deepen their understanding of the potentials offered by membranes for molecule separation and purification applications. The laboratory experiment can be performed during a 3 h activity with the purpose of (1) exposing students to a new and interesting field of advanced membrane separation technology. It not only (2) familiarizes them with the synthesis and self-assembly of nanowires into membranes, but it also (3) helps them to understand the membrane's important role in molecular separation application.